Process for igniting hydrocarbon materials present within oil-bearing formations



2,863,510 Patented Dec. 9, 1958 PROCESS FOR IGNITING HY DROCARBON MATE-RIALS PRESENT WITHIN OIL-BEARIN G FORMA- TIONS Harco J. Tadema andJohannes T. Quant, Amsterdam, I .Netherlands, assignors toShellDevelopment tl'ompnny,

New York, N. Y., a corporation of Delaware No Drawing. Application July25, 1955 Serial No. 524,304

Claims priority, application Netherlands July 3%), was

' 6 Claims. (Cl. 166-38) The invention relates to the production ofpetroleum and pertains more particularly to a process for igniting oil,oil residue or other combustible materials presentin an oil-bearingformation in the production of petroleum by means of undergroundcombustion.

It has previously been proposed to produce oil by the use of undergroundcombustion. In this method a part of the oil originally present in theoil-bearing formation is burnt. To this end, the oil is ignited in orthrough one or more wells, the combustion of the oil being subsequentlymaintained by forcing in air and attempting to produce the unburntportion of oil from one or more (the same or other) wells.

Various methods are known for igniting oil, oil residue, tarrysubstances, etc. present in the formation. To this end, highly heatedgases are usually introduced in a well and forced into the formation. Ithas also been proposed to ignite the oil by means of an electric currentor thermite bombs. It ,is, however, difl'icult to obtain a uniformcombustion of the oil in the formation by these methods. Furthermore,there is a considerable risk of the formation being clogged by depositsof solid combustion products and as a result of sintering caused by thevery high temperatures which occur.

It is therefore an object of the present invention to provide a methodof ignition which ensures a uniform combustion of the oil in theformation surrounding a well, without the formation being clogged bydeposits or sintering, since in this method the temperature does notincrease to such an extent that there is any possibility of theformation sintering.

According to the invention the combustible material (oil, oil residue,tar, etc.) in an oil-bearing formation is brought to the hightemperature required for combustion by introducing into a well andcontacting the oil-bearing formation therein with a liquid whichoxidizes relatively easily, together with, or followed by, a gaseousoxidant which under the operating conditions reacts spontaneously withthe liquid.

A part of the combustible material present in the formation, usuallyoil, may have collected in one or more wells which lead into theformation. Accordingly, the oil (oil residue, etc.) present in the wellsalso belongs to the combustible material which can be ignited accordingto the invention.

Although the desired result can often be obtained by introducing theliquid into a well, it is advisable, in some areas, to force the liquidinto the formation itself. The gaseous oxidant reacts with theoxidizable liquid, developing a high degree of heat, as a result ofwhich the heat required for ignition is developed at the very place (thebottom of the well and in the formation itself) where it is required forthe underground combustion which then follows. By forcing air into theformation afterwards, a uniform combustion of the oil surrounding thewell can be readily obtained.

In any case the relatively easily oxidizable liquid should be morereadily oxidizable" than the combustible material in the formation(measured under the same conditions),

The oxidizable liquid and the oxidant are chosen so that under theoperating conditions (of pressure and temperature in the well. or theformation) there is a spou-- taneous reaction between these substances.It is advisable, however, to use a combination which reactsat even lowertemperatures than those encountered in a well.

Suitable oxidizable liquids include: unsaturated aliphatic hydrocarbons,such 'as cracked distillates; cyclic hydrocarbons, such as turpentine,tetralin or decalin; unsaturated aliphatic or cyclic oxygen-containingcompounds, such as croton-aldehyde,,allylalcohol, furfural or linseedoil; aliphatic or cyclic nitrogen-containing, com: pounds, such asethylene diamine or anilineand phenylhydrazine. l

The liquid in question need not be a simple substance, but may consistof a mixture of chemical compounds; moreover, it may comprise a reactioninitiator, such as peroxide, or a catalyst, such as manganese resinate.The liquid may also be a suspension or an emulsion.

The gaseous oxidantshould be so chosen that, at least under theoperating conditions of pressure and temperature in the well or theformation, it reacts spontaneously with the liquid. Suitable substancesinclude oxygen,

ozone, gaseous nitrogen oxides, gases containing a.relatively highconcentration of such oxidants, and mixtures of such. gases.Occasionally (depending on the liquid and operating conditions used)ordinary air may also be .used, generally under high pressure.

Air is generally used for, maintaining the actual com: bustion of theoil. in the formation, which thus follows the ignition. If desired, thisair may contain an in,- creased or reduced oxygen content. Air with areduced oxygen content may be obtained by mixing it with inert gases.

If the formation contains a relatively large amount of water, it isoften advantageous first to expel the water from the neighborhood of thewell, for example, by using a gas drive since the water is more readilydisplaced than the more viscous oil.

If it is desired to initiate an underground combustion in a formationwhere a high temperature and/or a high pressure prevails naturally (viz.usually in a deep formation) the readily oxidizable liquid may sometimesbe omitted altogether, provided a gas is chosen as the oxidant whichcontains a very high concentration of oxygen (preferably pure orsubstantially pure oxygen), if desired, together with a gaseouscatalyst: or reaction initiator such as ozone or N0 The gaseous oxidantmay, for example, first be passed through an ozonizer which may, forexample, be provided in the well. The pressure at which the oxidant isintroduced. may be 25- atm. or even higher.

After the temperature required for igniting the oil is reached, ordinaryair may be injected instead of the said gaseous oxidant.

' We claim as our invention:

1. In the production of petroleum by means of underground combustion ofcombustible hydrocarbon material present in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing into said borehole andcontacting with said combustible material an amount of a readilyoxidizable material which is normally a liquid and a gaseous oxidantwhich reacts spontaneously at borehole conditions with said liquid toraise the temperature at said combustible materdial to its ignitionpoint with combustion taking place while the oxidizable liquid is inliquid form.

2. In the production of petroleum by means of underground combustion ofcombustible hydrocarbon material present in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing into said borehole anamount of a readily oxidizable material which is normally a liquid and agaseous oxidant which reacts spontaneously at borehole conditions withsaid liquid, and injecting said liquid and gaseous oxidant into saidoil-bearing formation so that they react with said combustible materialto raise the temperature thereof to its ignition point with combustiontaking place while the oxidizable liquid is in liquid form.

, 3. In the production of petroleum by means of underground combustionof combustible hydrocarbon material present'in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing into said borehole anamount of a readily oxidizable material which is normally a liquid and agaseous oxidant which reacts spontaneously at borehole conditions withsaid liquid, and injecting said liquid and gaseous oxidant into saidoilbearing formation so as to react with said combustible material toraise the temperature thereof to its ignition point with combustiontaking place while the oxidizable liquid is in liquid form, said gaseousoxidant being a gas containing at least 50 percent oxygen.

4. 'In the production of petroleum by means of underground combustion ofcombustible hydrocarbon materials present in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing into said borehole anamount of a readily oxidizable material which is normally a liquid and agaseous oxidant which reacts spontaneously at borehole conditions withsaid liquid, and injecting said liquid and gaseous oxidant into saidoilbearing formation so as to react with said combustible material toraise the temperature thereof to its ignition point with combustiontaking place while the oxidizable liquid is in liquid form, said oxidantbeing gaseous nitrogen oxides.

5. In the production of petroleum by means of underground combustion ofcombustible hydrocarbon material present in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing simultaneously into saidborehole an amount of a gaseous oxidant and an amount of a readilyoxidizable material which is normally a liquid, and injecting saidgaseous oxidant and liquid simultaneously into said oil-bearingformation so that they react spontaneously with said combustiblematerial to raise the temperature thereof to its ignition point withcombustion taking place while the oxidizable liquid is in liquid form.

6. In the production of petroleum by means of underground combustion ofcombustible hydrocarbon material present in an oil-bearing formationpenetrated by a borehole, the method of igniting said combustiblematerial comprising the steps of introducing simultaneously into saidborehole an amount of a gaseous oxidant and an amount of a readilyoxidizable material which is normally a liquid, and injecting saidgaseous oxidant and liquid simultaneously into said oil-bearingformation so that they react spontaneously with said combustiblematerial to raise the temperature thereof to its ignition point withcombustion taking place while the oxidizable liquid is in liquid form,said liquid being a cracked petroleum distillate capable of reducing theignition temperature of the combustible material.

References Cited in the file of this patent UNITED STATES PATENTS1,806,499 Ranney May 19, 1931 2,382,471 Frey Aug. 14, 1945 2,747,672Simm May 29, 1956

1. IN THE PRODUCTION OF PETROLEUM BY MEANS OF UNDERGROUND COMBUSTION OF COMBUSTIBLE HYDROCARBON MATERIAL PRESENT IN AN OIL-BEARING FORMATION PENETRATED BY A BOREHOLE, THE METHOD OF IGNITING SAID COMBUSTIBLE MATERIAL COMPRISING THE STEPS OF INTRODUCING INTO SAID BOREHOLE AND CONTACTING WITH SAID COMBUSTIBLE MATERIAL AN AMOUNT OF A READILY OXIDIZABLE MATERIAL WHICH IS NORMALLY A LIQUID AND A GASEOUS OXIDANT WHICH REACTS SPONTANEOUSLY AT BOREHOLD CONDITIONS WITH SAID LIQUID TO RAISE THE TEMPERATURE AT SAID COMBUSTIBLE MATERIAL TO ITS IGNITIOIN POINT WITH COMBUSTION TAKING PLACE WHILE THE OXIDIZABLE LIQUID IS IN LIQUID FORM. 